Electric utility companies have long been confronted with a requirement for providing excess generating capacity in order to accommodate peak loading periods. These periods occur for a variety of reasons related to home appliance use or industrial requirements. For example, widespread use of air-conditioning occurs on hot days, while heating related loads occur during winter periods. Industrial utilization, for the most part, occurs during specific working hours and all such concentrations of use combine to develop demand peak periods.
To recoupe the costs associated with the additional generating capacity required, utility companies have resorted to a variety of billing structure approaches related to peak period power use. One such approach, sometimes referred to as "billing demand", elevates the rate structure to penalize a consumer whenever the demand load of a user exceeds a predetermined maximum value. Monitoring for such billing is carried out by demand meters which provide a billing output reflecting both higher and lower demand load rates.
Industry, in particular, has turned to the use of load monitoring and shedding schemes to control the higher energy costs resulting from peak demands. The techniques for carrying out such control usually are somewhat involved, microprocessors and the like often being utilized to provide a programmed priority control of load shedding. For the home or farm environment, however, a flexible, relatively low cost load shedding approach is required. To find acceptance in such non-industrialmarkets, the load shedding approach should permit the consumer to select those loads or appliances which are to be controlled and assign a use priority to them such that more important appliances will be shut down the least. In a farm environment, water heaters, for example associated with milking facilities will have a lower priority, while milking operation equipment will be assigned a very high priority. Conversely, feeding operation equipment including silo loaders, elevators or augers would be assigned a lower priority. In the home, such implements as water heaters and clothes dryers would be assigned a lower priority, while electric stoves would be assigned higher priority. Similarly, baseboard heaters could be arranged with priorities related to their location. Another desirable attribute for such a control arrangement will be concerned with the reinstatement of a load. For example, should a load which has been shed have a relatively low incremental value with respect to the total maximum demand, upon the lowering of total loads to an extent permitting this smaller load to return, the system should so react. However, when a drop in the total load is such that a higher priority load can be reinstated, then the low priority load should be held off while higher priority loadings are returned to service.